There is a radio frequency identification (RFID) system as an example of a communication system in which local devices exchange a radio frequency signal with each other. RFID is a technique that automatically recognizes data stored in a tag, a label, or a card mounting a micro chip therein. In an RFID system, tags are attached to products or objects to be managed, identification information of the objects and ambient environmental information are recognized to collect, store, process, and track information for respective objects, so that various services such as positioning, remote processing, and management for the objects, and information exchange therebetween may be provided. The RFID may simultaneously recognize a plurality of tags in a non-contact manner, store large capacity data, and be semi-permanently used, and a recognition time thereof is short. Accordingly, the RFID is attracting attention as a main technology for the next generation for solving the problems of a conventional barcode or a magnetic recognition device and improving convenience of use.
An RFID system includes a tag, a reader, and a server (middleware and application service platform), and is used to operatively cooperate with a wire/wireless communication network. The tag has information capable of recognizing objects and is positioned on the objects. The reader collects and processes information regarding the objects, and has a communication function transmitting the information to the server. The server performs application processing using the information regarding the objects.
RFID reader transmits power and a command to the tag as a carrier signal, receives a response from the tag, and restores the signal. In this case, the power enables a passive tag to be operated. The RFID reader includes an RF analog unit and a digital signal processing control unit. The RF analog unit includes a power amplifier and a frequency up-mixer transferring power and data to an antenna, a low noise amplifier and an analog signal processor restoring a response signal received by the antenna from the tag. The digital signal processing control unit includes an encoder, a decoder, a clock generation circuit, a memory, a processor, and a host interface device.
In order to revitalize the market of RFID, it is necessary to reduce the cost of the tag and the reader. In a receiver of the reader, since a circuit compensating for a phase of a tag signal is complicated, it becomes an obstacle in a cost reduction of the reader. Moreover, when the noise is included in the tag signal, it is difficult to exactly decode the data. A transmission speed of the tag signal is different from an expected speed, it is difficult to exactly decode the data.